public void startup(Context context) {
   this.context = context;
   SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
   for (AbstractSensor sensor : sensors) {
     try {
       boolean savedstate = prefs.getBoolean(sensor.getClass().getName(), true);
       Log.d(SensorRegistry.TAG, sensor.getClass().getName() + ": " + savedstate);
       if (savedstate) sensor.enable();
     } catch (Exception e) {
       sensor.disable();
       Log.d(SensorRegistry.TAG, e.toString());
       StringWriter sw = new StringWriter();
       PrintWriter pw = new PrintWriter(sw);
       e.printStackTrace(pw);
       Log.d(SensorRegistry.TAG, sw.toString());
     }
   }
 }